Thesis (MSc (Geography and Environmental Studies))--University of Stellenbosch, 2005. / 81 Leaves printed on single pages i-xi, preliminary pages and numbered pages 1- 70. Includes bibliography, list of tables and list of figures. / Digitized at 300 dpi color PDF format (OCR), using KODAK i 1220 PLUS scanner. / ENGLISH ABSTRACT: Geological field mapping is often limited by logistical and cost constraints as well as the scope and extent of observations possible using ground-based mapping. Remote sensing offers, among others, the advantages of an increased spectral range for observations and a regional perspective of areas under observation. This study aimed to determine the accuracy of a collection of image classification techniques when applied to ASTER reflectance data. Band rationing, the Crosta Technique, Constrained Energy Minimization, Spectral Correlation Mapping and the Maximum Likelihood Classifier were evaluated for their efficiency in detecting and discriminating between greenstone and granitoid material. The study area was the Archaean Barberton Greenstone Belt in the eastern Mpumalanga Province, South Africa. ASTER reflectance imagery was acquired and pre-processed. Training and reference data was extracted from the image through visual inspection and expert knowledge. The training data was used in conjunction with USGS mineral spectra to train the five classification algorithms using the ERDAS's software package. This resulted in abundance images for the target materials specified by the training data. The Maximum Likelihood Classifier produced a classified thematic map. The reference data was used to perform a rigorous classification accuracy assessment procedure. All abundance images were thresholded to varying levels, obtaining accuracy statistics at every level. In so doing, threshold levels could be defined for every abundance image in such a way that the reliability of the classification was optimized. For each abundance image, as well as for the output map of the Maximum Likelihood Classifier, user's- and producer's accuracies as well as kappa statistics were derived and used as comparative measures of efficiency between the five techniques. This information was also used to assess the spectral separability of the target materials. The Maximum Likelihood Classifier outperformed the other techniques significantly, achieving an overall classification accuracy of 81.1% and an overall kappa value of 0.748. Greenstone rocks were accurately discriminated from granitoid rocks with accuracies between 72.9% and 98.5%, while granitoid rocks showed very poor ability to be accurately distinguished from each other. The main recommendations from this study are that thermal infrared and gamma-ray data be considered, together with better vegetation masking and an investigation into object orientated techniques. / AFRIKAANSE OPSOMMING: Geologiese veldkartering word algemeen beperk deur logistiese en koste-verwante faktore, sowel as die beperkte bestek waartoe waarnemings met veld-gebasseerde tegnieke gemaak kan word. Afstandswaarneming bied, onder andere, 'n vergrote spekrale omvang vir waarnemings en 'n regionale perspektief van die area wat bestudeer word. Hierdie studie was gemik daarop om die akkuraatheid van 'n versameling beeld-klassifikasie tegnieke, toegepas op ASTER data, te bepaal. Bandverhoudings, die Crosta Tegniek, "Constrained Energy Minimization", Spektrale Korrellasie Kartering, en Maksimum Waarskynlikheid Klassifikasie is evalueer op grond van hul vermoë om groensteen en granitoied-rotse op te spoor en tussen hulle te onderskei. Die studiegebied was die Argalese Barberton Groensteengordel in die oostelike Mpumalanga Provinsie in Suid Afrika. 'n ASTER refleksie beeld is verkry, waarop voorverwerking uitgevoer is. Opleidings- en verwysingsdata is van die beeld verkry deur visuele inspeksie en vakkundige kennis. Die opleidingsdata is saam met VSGO mineraalspektra gebruik om die vyf klassifikasie algoritmes met behulp van die ERDAS sagteware pakket op te lei. Die resultaat was volopheidsbeelde vir die teikenmateriale gespesifiseer in die opleidingsdata. Die Maksimum Waarskynlikheid algoritme het 'n geklassifiseerde tematiese beeld gelewer. Met behulp van die verwysingsdata is 'n streng akkuraatheidstoetsing prosedure uitgevoer. Vir alle volopheidsbeelde is 'n reeks drempelwaardes gestel, en by elke drempelwaarde is akkuraatheidsstatistieke afgelei. Op hierdie manier kon 'n drempelwaarde vir elke volopheidsbeeld vasgestel word sodat die drempelwaarde die betroubaarheid van die klassifikasie optimeer. Vir elke volopheidsbeeld, asook vir die tematiese kaart verkry van die Maksimum Waarskynlikheid klassifikasie, is gebruikers- en produsent-akkuraathede en kappa statistieke bereken. Hierdie waardes is gebruik as vergelykende maatstawwe van akkuraatheid tussen die vyf tegnieke, asook van die spektrale skeibaarheid van die onderskeie teikenmateriale. Die Maksimum Waarskynlikheid klassifikasie het die beste resultate gelewer, met 'n algehele klassifikasie akkuraatheid van 81.1%, en 'n gemiddelde kappa waarde van 0.748. Groensteenrotse kon met hoë akkuraathede van tussen 72.9% en 98.5% van granitoiedrotse onderskei word, terwyl granitoiedrotse 'n swak vermoë getoon het om van mekaar onderskei te word. Die belangrikste aanbevelings vanuit hierdie studie is dat termiese uitstralingdata asook gamma-straal data geimplimenteer word. Beter verwydering van plantegroei en 'n studie na die lewensvatbaarheid van objekgeorienteerde metodes word ook aanbeveel.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The source of the K2O in the K2O-rich ~3.45 Ga felsic intrusive rocks of the H6 unit in the Hooggenoeg Formation of the Onverwacht Group in the Barberton Granite Greenstone Terrain (BGGT) is examined in this study. This is of particular research interest because the Paleoarchaean rock record is considered to lack K2O-rich magmatic rocks. Previous studies on the felsic igneous rocks of the H6 unit have proposed that these rhyolites are K-metasomatised eruptive equivalents of the sodium-rich ~3.45 Ga TTGs of the BGGT and that the K-feldspar crystals in the rocks formed as a consequence of subsolidus replacement of plagioclase by K-feldspar. Furthermore, the timing of K-metasomatism has previously been related to the formation of the Buck Ridge Chert (BRC), which overlies the H6 unit. However, it has recently been demonstrated from granitic clasts in the conglomerate layer at the base of the Moodies sucession that K2O-rich magmatic rocks formed concurrently with TTG magmas during each of three episodes of TTG magmatism observed in the BGGT. Consequently, the hypothesis of a metasomatic origin for the K2O-rich character of the felsic rocks of the H6 unit requires further examination. Previous studies of the chemistsry of felsic volcanic rocks within the H6 unit were based on relatively low numbers of samples. This study has examined a substantial set of the freshest material available. Two varieties of felsic volcanic rocks were identified; K2O-rich, CaO-poor, Na2O-poor rhyolites and Na2O-rich, CaO-poor, K2O-poor Na-rhyolites. The K2O- rich rhyolite variety is dominant. Consequently, it is possible that the K2O-rich character of these rocks represents a primary magmatic signature. However, this judgment is complicated by the presence of a greenschist-facies metamorphic overprint at 3.2 Ga, which has resulted in complete replacement of micrystalline groundmass and partial replacement of the phenocryst assemblages by greenschist- and sub-greenschist-facies mineral assemblages, which undoubtedly allowed possible shifts in chemical compositions In this thesis, I test the source of K2O in these rocks by using the porphyritic textures of the rocks as an indication of the primary composition of the magmas they were formed from. These textures are typically defined by K-feldspar or albite and quartz phenocrysts within a microcrystalline groundmass. The rocks containing albite are Na-rich (Na-rhyolites) whereas the rocks defined by K-feldspar phenocrysts are rhyolites. XRD study of the structural state of the K-feldspar phenocrysts in the rhyolites indicates that these crystals are orthoclase and intermediate microcline, i.e. medium temperature K-feldspar polymorphs. The modal proportions of K-feldspar, quartz and microcrystalline groundmass in the rhyolites were calculated by using image analysis software. The compositions of the feldspar minerals were determined by electron beam analysis. Minimum bulk rock K2O content of the rhyolites were calculated from the proportions of K-feldspar crystals and their compositions. Even where the proportion of K-feldspar phenocrysts is relatively low (~ 30%), the calculated minimum bulk-rock K2O content is still above 5 wt%. The HREE slope (GdN/LuN) of the felsic porphyritic rocks of the H6 rhyolites is similar to that of ~3.45 Ga TTG plutons and steeper than that of granitic clasts of identical age contained in the basal conglomerate of the Moodies Group. Hence this study has illustrated that the rhyolites of the H6 unit were primary K-feldspar-rich, K2O-rich magmas that formed contemporarily with the ~3.45 Ga TTGs. This implicitly means that rhyolitic volcanism was more wide spread than previously thought in the Paleoarchaean and that it occurred together with the intrusion of the ~3.45 Ga TTGs in the BGGT. / AFRIKAANSE OPSOMMING: Die bron van die K2O in die K2O-ryk ~ 3,45 Ga felsiese vulkaniese rotse van die H6-eenheid in die Hooggenoeg formasie van die Onverwacht Groep in die Barberton Graniet Groensteen Terrein (BGGT) is in hierdie studie ondersoek. Dit is van besondere navorsingsbelang omdat die Paleoargeïse gesteenterekord beskou word as vry van magmatiese K2O ryke gesteentes. Vorige studies oor die felsiese vulkaniese rotse van die H6 eenheid het voorgestel dat hierdie rioliete K-gemetasomatiese eruptiewe ekwivalente van die natrium-ryke ~ 3,45 Ga TTGs van die BGGT is en dat die K-veldspaat kristalle in die gesteentes gevorm is as gevolg van subsolidus vervanging van plagioklaas deur K-veldspaat. Verder is die tydsberekening van K-metasomatisme voorheen gekoppel aan die vorming van die Buck Ridge Chert (BRC) wat die felsiese H6 eenheid bedek. Dit is egter onlangs aangetoon dat K2O-ryke magmatiese rotse gelyktydig met TTG magmas gevorm is tydens elk van drie episodes van TTG magmatisme waargeneem in die BGGT. Gevolglik vereis die hipotese van 'n metasomatiese oorsprong vir die K2O-ryke karakter van die felsiese gesteentes van die H6 eenheid verdere ondersoek. Vorige studies van die felsiese vulkaniese gesteentechemie in die H6 eenheid is gebaseer op 'n relatief klein getal monsters. Hierdie studie het 'n aansienlike stel van die varsste materiaal beskikbaar vir analise ondersoek. Twee variëteite van peralumineuse felsiese vulkaniese gesteentes naamlik 'n K2O-ryk, CaO-arm, Na2O-arm rioliet en Na2O-ryk, CaO-arm, K2O-arm Na-rioliet. Die K2O-ryke rioliet variëteit is meer oorheersend as die Na-rioliete. Dit is dus moontlik dat die K2O-ryk karakter van hierdie rotse 'n primêre magmatiese kenmerke verteenwoordig. Hierdie uitspraak is egter bemoeilik deur die teenwoordigheid van 'n groenskisfasies metamorfe oorprint op 3,2 Ga, wat gelei het tot die volledige vervanging van mikrokrisstalyne grondmassa en gedeeltelike vervanging van fenokrist samestellings deur groenskis en sub-groenskisfasies minerale samestellings en wat ongetwyfeld toegelaat het vir 'n moontlike verskuiwing in chemiese samestelling. In hierdie tesis toets ek die bron van K2O in hierdie gesteentes deur gebruik te maak van die vulkaniese teksture van die gesteentes as 'n aanduiding van die primêre samestelling van die magmas waaruit hulle gevorm het. Hierdie teksture word gewoonlik gedefinieer deur K-veldspaat of albiet en kwarts fenokriste binne 'n grondmassa van wat vroeërglasoorblyfsels was. Die rotse wat albiet bevat is Na-ryk (Na-rioliete) terwyl die rotse gedefinieer deur K-veldspaat fenokriste rioliete is. XRD studie van die strukturele toestand van die K-veldspaat fenokriste in die rioliete dui aan dat hierdie kristalle ortoklaas en intermediêre mikroklien is, dit wil sê die hoër temperatuur K-veldspaat polimorfe. Die modale proporsies van K-veldspaat, kwarts en glasoorblyfsels in die rioliete is akkuraat bereken deur gebruik te maak van beeld analise sagteware. Verder is die samestellings van die veldspaat minerale bepaal deur die elektronstraal analise. Minimum grootmaat rots K2O inhoud van die rioliet is berekén vanaf die fase verhouding van K-veldspaat en hul komposisies. Resultate dui daarop dat selfs waar die verhouding van K-veldspaat phenocrysts is relatief laag (~ 30%), die berekende minimum K2O grootmaat rots samestelling is nog steeds bo 5 wt%. Die REE-helling (GDN / Lun) van felsiese porphyritic rotse van die H6 is soortgelyke relatief tot die REE helling van ~ 3,45 Ga TTGs en steiler REE helling relatief tot granitiese klaste vervat in die basale konglomeraat van die Moodies-groep. Dus het hierdie studie getoon dat die rioliete van die H6-eenheid primêre K-veldspaat-ryke, K2O-ryke en peralumineuse magmas was wat gevorm is terselfdertyd met die ~3,45 Ga TTGs. Dit beteken implisiet dat riolitiese vulkanisme meer wyd verspreid was as wat voorheen gedink is in die Paleoargeïkum en dat dit tesame met die indringing van die ~ 3,45 Ga TTGs in die BGGT plaasgevind het.

No / The ESA/Roscosmos ExoMars rover will be launched in 2018. The primary aim of the mission will be to find evidence of extinct or extant life by extracting samples from the subsurface of Mars. The rover will incorporate a drill that is capable of extracting cores from depths of up to 2 m, a Sample Preparation and Distribution System (SPDS) that will crush the core into small grains and a suite of analytical instruments. A key component of the analytical suite will be the Raman Laser Spectrometer (RLS) that will be used to probe the molecular and mineralogical composition of the samples. In this work we consider the capability of the proposed Raman spectrometer to detect reduced carbon (possibly associated with evidence for extinct life) and to identify the level of thermal alteration/maturity. The Raman analysis of 21 natural samples of shale (originating from regions exhibiting different levels of thermal maturity) is described and it is shown that reduced carbon levels as low as 0.08% can be readily detected. It is also demonstrated that the Raman spectra obtained with the instrument can be used to distinguish between samples exhibiting high and low levels of thermal maturity and that reduced carbon can be detected in samples exposed to significant levels of oxidation (as expected on the surface of Mars). (C) 2014 Published by Elsevier Ltd.